In the study of \(e^+e^-\rightarrow \pi ^+\pi ^-J/\psi \) , a distinct charged structure,
\(Z_c(3900)^{\pm }\) , was observed in the \(\pi ^\pm J/\psi \)  spectrum by the
BESIII [1]} and Belle [2]} experiments, and confirmed
shortly thereafter with CLEO-c data [3]}. A similar charged
structure but with a slightly higher mass, \(Z_{c}(4020)^{\pm }\) , was soon reported
in \(e^+e^-\rightarrow \pi ^+\pi ^-h_c\)  [4]} by BESIII. As
there are at least four quarks within these two charmoniumlike structures, they
are interpreted as either tetraquark states, \(D\bar{D}^*\)  (or \(D^*\bar{D}^*\) ) molecules,
hadrocharmonia, or other configurations [5]}. More recently,
charged structures in the same mass region were observed via their
decays into charmed meson pairs, including the charged \(Z_c(4025)^{\pm }\)  in \(e^+e^-\rightarrow \pi ^{\pm } (D^*\bar{D}^*)^{\mp }\)  [6]} and the charged \(Z_c(3885)^{\pm }\)  in \(e^+e^-\rightarrow \pi ^{\pm } (D\bar{D}^*)^{\mp }\)  [7]}. These structures together
with the recently confirmed \(Z(4430)^-\)  [8]}, [9]}, [10]} and
similar structures observed in the bottomonium system [11]} indicate
that a new class of hadrons has been observed.
An important question is whether
all these charged structures are part of isospin \(I=1\) 
triplets, in which case neutral partners with \(I_z = 0\)  should also
be found.
Evidence for a neutral \(Z_c(3900)\)  was observed in \(e^+e^-\rightarrow \pi ^0\pi ^0 J/\psi \)  process with CLEO-c data
at center-of-mass energy (CME) \(\sqrt{s}\) =4.17 GeV [3]}. A neutral structure, the \(Z_c(4020)^{0}\) ,
is expected to couple to the \(\pi ^0 h_c\)  final state and be produced for in \(e^+e^-\rightarrow \pi ^{0}\pi ^{0}h_{c}\)  processes.
